Document Type : Original Article
Authors
1
Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran
2
Mining Department, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran
10.22077/jt.2025.8266.1188
Abstract
The metabasites in the Meydanak area are part of the Azna-Doroud metamorphic complex, which belongs to the Sanandaj-Sirjan structural zone. Metabasic (amphibolite) rocks have undergone metamorphic and deformation phases accompanied by migmatization with a low melt component and are classified as metatexite. Structures such as schlieren, ophthalmic, diktyonitic, and stromatic (from filmic to nebulitic) are observed in these migmatites. The main minerals in these rocks include amphibole, plagioclase, and quartz, while secondary minerals are chlorite, epidote, biotite, titanite, and opaque. The migmatites exhibit alternating paleosome and leucosome bands, aligned with the mylonitic foliation. In addition to migmatization, amphibolites are significantly influenced by ductile deformation. Evidence of this deformation in quartz crystals includes undulose extinction, subgrains and neograins formation, dynamic recrystallization (BLG, SGR, GBM), and grain boundary deformation. Deformation twins and undulous extinction further indicate deformation in plagioclase and amphibole crystals. The presence of these rocks in the shear zone has resulted in mylonitic microstructures such as foliation, lineation, core-mantle porphyroclasts, synthetic and antithetic microfractures, and fish-like amphibole grains. Microstructures show deformation and metamorphism have predominantly occurred within amphibolite facies, with some degree of greenschist facies. The alternating leucosome and paleosome bands, aligned with the foliation, along with other evidence such as the amorphous nature of amphibole grains, quartz-filled amphibole crystals, and straight, smooth boundaries between plagioclase and quartz crystals, indicate that deformation occurred concurrently with migmatization. Overall, microstructural evidence suggests the occurrence of ductile and brittle deformation events at temperatures of more than 700 °C (GBAR) to 300 °C (BLG).
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